1. Field of the Invention
The present invention is directed in general to the field of electric circuits. In one aspect, the present invention relates to a switch arrangement for providing a switch failure signal.
2. Description of the Related Art
Switching circuits use field effect transistor (FET) devices to control the application of power in a variety of different applications, such as power switching applications for driving headlights, injector or braking valves and other automotive power supply applications. Increasingly, smart semiconductor switches have been developed for dynamically adjusting a load current and/or providing a current protection function by immediately switching OFF the load current upon sensing a current surge. For example, Freescale offers smart semiconductor switches in the MC33982 or MC33984 products as part of the eXtreme switch family of products. But even with high quality fabrication and testing processes that prevent or detect device defects, some of the switch FETs can become defective after a part has been shipped because of particle level defects and/or because of “over stress” conditions that are applied in the field, resulting in a damaged FET gate that is resistively shorted to the FET drain. When the switch enters a sleep mode and the damaged FET gate is allowed to float, the resistive gate-drain short will cause the floating gate voltage to rise toward the supply voltage at the drain, causing the FET to become partially enhanced so that the FET operates in the linear region. In the linear mode of operation, the FET can dissipate a large amount of heat, possibly causing a destructive thermal event. Currently, there is no way to notify the system of a switching circuit failure caused by a gate-drain short, and there is no way to prevent the failure from progressing into a thermal event.
Accordingly, a need exists for an improved switching circuit, system and method of operation that addresses various problems in the art that have been discovered by the above-named inventors where various limitations and disadvantages of conventional solutions and technologies will become apparent to one of skill in the art after reviewing the remainder of the present application with reference to the drawings and detailed description which follow, though it should be understood that this description of the related art section is not intended to serve as an admission that the described subject matter is prior art.